Raise a warning instead of an error for a type ascription on a patter…

…n other than a variable or a number literal. This partially reverts the changes from scala#16150. This change is motivated by not breaking source compatibility for a number of projects in the Open Community Build.
dotty-staging · May 10, 2023 · 6d8d23b · 6d8d23b
1 parent 982ce3f
commit 6d8d23b
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Showing 8 changed files with 76 additions and 19 deletions.
diff --git a/compiler/src/dotty/tools/dotc/parsing/Parsers.scala b/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
@@ -2871,14 +2871,14 @@ object Parsers {
       if (isIdent(nme.raw.BAR)) { in.nextToken(); pattern1(location) :: patternAlts(location) }
       else Nil
 
-    /**  Pattern1     ::= PatVar Ascription
-     *                  | [‘-’] integerLiteral Ascription
-     *                  | [‘-’] floatingPointLiteral Ascription
-     *                  | Pattern2
+    /**  Pattern1     ::= Pattern2 [Ascription]
      */
     def pattern1(location: Location = Location.InPattern): Tree =
       val p = pattern2()
-      if (isVarPattern(p) || p.isInstanceOf[Number]) && in.isColon then
+      if in.isColon then
+        val isVariableOrNumber = isVarPattern(p) || p.isInstanceOf[Number]
+        if !isVariableOrNumber then
+          warning(em"Only variable and number literal patterns can have type ascriptions")
         in.nextToken()
         ascription(p, location)
       else p

diff --git a/docs/_docs/internals/syntax.md b/docs/_docs/internals/syntax.md
@@ -314,10 +314,7 @@ TypeCaseClauses   ::=  TypeCaseClause { TypeCaseClause }
 TypeCaseClause    ::=  ‘case’ (InfixType | ‘_’) ‘=>’ Type [semi]
 
 Pattern           ::=  Pattern1 { ‘|’ Pattern1 }                                Alternative(pats)
-Pattern1          ::=  PatVar ‘:’ RefinedType                                   Bind(name, Typed(Ident(wildcard), tpe))
-                    | [‘-’] integerLiteral ‘:’ RefinedType                      Typed(pat, tpe)
-                    | [‘-’] floatingPointLiteral ‘:’ RefinedType                Typed(pat, tpe)
-                    |  Pattern2
+Pattern1          ::=  Pattern2 [‘:’ RefinedType]                               Bind(name, Typed(Ident(wildcard), tpe))
 Pattern2          ::=  [id ‘@’] InfixPattern [‘*’]                              Bind(name, pat)
 InfixPattern      ::=  SimplePattern { id [nl] SimplePattern }                  InfixOp(pat, op, pat)
 SimplePattern     ::=  PatVar                                                   Ident(wildcard)

diff --git a/docs/_docs/reference/syntax.md b/docs/_docs/reference/syntax.md
@@ -312,10 +312,7 @@ TypeCaseClauses   ::=  TypeCaseClause { TypeCaseClause }
 TypeCaseClause    ::=  ‘case’ (InfixType | ‘_’) ‘=>’ Type [semi]
 
 Pattern           ::=  Pattern1 { ‘|’ Pattern1 }
-Pattern1          ::=  PatVar ‘:’ RefinedType
-                    | [‘-’] integerLiteral ‘:’ RefinedType
-                    | [‘-’] floatingPointLiteral ‘:’ RefinedType
-                    |  Pattern2
+Pattern1          ::=  Pattern2 [‘:’ RefinedType]
 Pattern2          ::=  [id ‘@’] InfixPattern [‘*’]
 InfixPattern      ::=  SimplePattern { id [nl] SimplePattern }
 SimplePattern     ::=  PatVar

diff --git a/tests/neg/i10994.scala → ...g-custom-args/fatal-warnings/i10994.scala b/tests/neg/i10994.scala → ...g-custom-args/fatal-warnings/i10994.scala
diff --git a/tests/neg/i15893.scala → ...g-custom-args/fatal-warnings/i15893.scala b/tests/neg/i15893.scala → ...g-custom-args/fatal-warnings/i15893.scala
@@ -22,7 +22,7 @@ transparent inline def transparentInlineMod2(inline n: NatT):  NatT = inline n m
   case Succ(Zero()) => Succ(Zero())
   case Succ(Succ(predPredN)) => transparentInlineMod2(predPredN)
 
-def dependentlyTypedMod2[N <: NatT](n: N): Mod2[N] = n match // exhaustivity warning; unexpected
+def dependentlyTypedMod2[N <: NatT](n: N): Mod2[N] = n match
   case Zero(): Zero => Zero() // error
   case Succ(Zero()): Succ[Zero] => Succ(Zero()) // error
   case Succ(Succ(predPredN)): Succ[Succ[_]] => dependentlyTypedMod2(predPredN) // error
@@ -57,5 +57,5 @@ inline def transparentInlineFoo(inline n: NatT): NatT = inline transparentInline
   println(transparentInlineMod2(Succ(Succ(Succ(Zero()))))) // prints Succ(Zero()), as expected
   println(transparentInlineFoo(Succ(Succ(Succ(Zero()))))) // prints Zero(), as expected
   println(dependentlyTypedMod2(Succ(Succ(Succ(Zero()))))) // runtime error; unexpected
-//  println(inlineDependentlyTypedMod2(Succ(Succ(Succ(Zero()))))) // doesn't compile; unexpected
-//  println(transparentInlineDependentlyTypedMod2(Succ(Succ(Succ(Zero()))))) // doesn't compile; unexpected
+  println(inlineDependentlyTypedMod2(Succ(Succ(Succ(Zero()))))) // prints Succ(Zero()), as expected
+  println(transparentInlineDependentlyTypedMod2(Succ(Succ(Succ(Zero()))))) // prints Succ(Zero()), as expected
diff --git a/tests/pending/run/i15893.scala b/tests/pending/run/i15893.scala
@@ -24,7 +24,7 @@ transparent inline def transparentInlineMod2(inline n: NatT):  NatT = inline n m
   case Succ(Zero()) => Succ(Zero())
   case Succ(Succ(predPredN)) => transparentInlineMod2(predPredN)
 */
-def dependentlyTypedMod2[N <: NatT](n: N): Mod2[N] = n match // exhaustivity warning; unexpected
+def dependentlyTypedMod2[N <: NatT](n: N): Mod2[N] = n match
   case Zero(): Zero => Zero()
   case Succ(Zero()): Succ[Zero] => Succ(Zero())
   case Succ(Succ(predPredN)): Succ[Succ[_]] => dependentlyTypedMod2(predPredN)
@@ -61,5 +61,5 @@ inline def transparentInlineFoo(inline n: NatT): NatT = inline transparentInline
   println(transparentInlineFoo(Succ(Succ(Succ(Zero()))))) // prints Zero(), as expected
 */
   println(dependentlyTypedMod2(Succ(Succ(Succ(Zero()))))) // runtime error; unexpected
-//  println(inlineDependentlyTypedMod2(Succ(Succ(Succ(Zero()))))) // doesn't compile; unexpected
-//  println(transparentInlineDependentlyTypedMod2(Succ(Succ(Succ(Zero()))))) // doesn't compile; unexpected
+//  println(inlineDependentlyTypedMod2(Succ(Succ(Succ(Zero()))))) // prints Succ(Zero()), as expected
+//  println(transparentInlineDependentlyTypedMod2(Succ(Succ(Succ(Zero()))))) // prints Succ(Zero()), as expected
diff --git a/tests/pos/i10994.scala b/tests/pos/i10994.scala
@@ -0,0 +1,2 @@
+def foo = true match
+  case (b: Boolean): Boolean => ()
diff --git a/tests/pos/i15893.scala b/tests/pos/i15893.scala
@@ -0,0 +1,61 @@
+sealed trait NatT
+case class Zero() extends NatT
+case class Succ[+N <: NatT](n: N) extends NatT
+
+type Mod2[N <: NatT] <: NatT = N match
+  case Zero => Zero
+  case Succ[Zero] => Succ[Zero]
+  case Succ[Succ[predPredN]] => Mod2[predPredN]
+
+def mod2(n: NatT):  NatT = n match
+  case Zero() => Zero()
+  case Succ(Zero()) => Succ(Zero())
+  case Succ(Succ(predPredN)) => mod2(predPredN)
+
+inline def inlineMod2(inline n: NatT):  NatT = inline n match
+  case Zero() => Zero()
+  case Succ(Zero()) => Succ(Zero())
+  case Succ(Succ(predPredN)) => inlineMod2(predPredN)
+
+transparent inline def transparentInlineMod2(inline n: NatT):  NatT = inline n match
+  case Zero() => Zero()
+  case Succ(Zero()) => Succ(Zero())
+  case Succ(Succ(predPredN)) => transparentInlineMod2(predPredN)
+
+def dependentlyTypedMod2[N <: NatT](n: N): Mod2[N] = n match
+  case Zero(): Zero => Zero() // warning
+  case Succ(Zero()): Succ[Zero] => Succ(Zero()) // warning
+  case Succ(Succ(predPredN)): Succ[Succ[_]] => dependentlyTypedMod2(predPredN) // warning
+
+inline def inlineDependentlyTypedMod2[N <: NatT](inline n: N): Mod2[N] = inline n match
+  case Zero(): Zero => Zero() // warning
+  case Succ(Zero()): Succ[Zero] => Succ(Zero()) // warning
+  case Succ(Succ(predPredN)): Succ[Succ[_]] => inlineDependentlyTypedMod2(predPredN) // warning
+
+transparent inline def transparentInlineDependentlyTypedMod2[N <: NatT](inline n: N): Mod2[N] = inline n match
+  case Zero(): Zero => Zero() // warning
+  case Succ(Zero()): Succ[Zero] => Succ(Zero()) // warning
+  case Succ(Succ(predPredN)): Succ[Succ[_]] => transparentInlineDependentlyTypedMod2(predPredN) // warning
+
+def foo(n: NatT): NatT = mod2(n) match
+  case Succ(Zero()) => Zero()
+  case _ => n
+
+inline def inlineFoo(inline n: NatT): NatT = inline inlineMod2(n) match
+  case Succ(Zero()) => Zero()
+  case _ => n
+
+inline def transparentInlineFoo(inline n: NatT): NatT = inline transparentInlineMod2(n) match
+  case Succ(Zero()) => Zero()
+  case _ => n
+
+@main def main(): Unit =
+  println(mod2(Succ(Succ(Succ(Zero()))))) // prints Succ(Zero()), as expected
+  println(foo(Succ(Succ(Succ(Zero()))))) // prints Zero(), as expected
+  println(inlineMod2(Succ(Succ(Succ(Zero()))))) // prints Succ(Zero()), as expected
+  println(inlineFoo(Succ(Succ(Succ(Zero()))))) // prints Succ(Succ(Succ(Zero()))); unexpected
+  println(transparentInlineMod2(Succ(Succ(Succ(Zero()))))) // prints Succ(Zero()), as expected
+  println(transparentInlineFoo(Succ(Succ(Succ(Zero()))))) // prints Zero(), as expected
+  println(dependentlyTypedMod2(Succ(Succ(Succ(Zero()))))) // runtime error; unexpected
+  println(inlineDependentlyTypedMod2(Succ(Succ(Succ(Zero()))))) // prints Succ(Zero()), as expected
+  println(transparentInlineDependentlyTypedMod2(Succ(Succ(Succ(Zero()))))) // prints Succ(Zero()), as expected